The present invention relates to oil pumps, and more particularly to a suction and pressure pipe arrangement for oil pumps.
Pumps having a positive delivery system, such as gear-type rotary pumps, are advantageously used as lubricating oil pumps for turbomachinery especially for steam turbo machines. These pumps, which typically have a great reliability of operation, may be driven by the turbomachinery to deliver oil without substantial difficulty and without the need for an auxiliary drive even at a relatively low speed of rotation of the turbo-machinery.
The presence of pressurized lubricating oil pipe lines, however, provides a potential fire hazard. Accordingly, regulations specify that the pressurized lines must be encased by a pipe line which is not under pressure in order to divert any leaking oil to a safe area.
After a turbomachine is shut down, it may take up to one hour for the rotor to stop turning. During the deceleration of the rotor, pressurized oil is being delivered to the turbomachine. In this way, a hazardous condition results if a fire should develop. Therefore, lubricating oil lines, and especially the pressurized pipe line from the oil pump, present sources of danger within the system, since necessary lubricating oil is being supplied to bearing of the turbomachine until the rotor of the turbine actually reaches a standstill.
A known volumetric oil pump uses a foot valve, which is installed in a suction manifold, to supply oil to the turbomachine. An auxiliary oil pump which fills the main oil pump by way of both the suction manifold and a filter subjects the main pump to oil pressure even before the start of the turbo machinery. The foot valve therefore allows the pump to be pressurized prior to the start up of the turbomachine. Accordingly, the suction manifold of a pump having a foot valve can not be considered to provide a non-pressurized shielding.
The difficulties of the known devices have been avoided to some extent by an arrangement in which oil pumps, which are not provided with a foot valve, are filled up by a vacuum pump.
Volumetric gear-driven pumps, as previously known, generally provide a suction lift of from 4 to 6 meters which is obtained by a tooth crown having a peripheral tooth velocity ranging from 8 to 12 meters per second. Such a peripheral tooth velocity results in a relatively high speed for a gear-driven pump. In order to more fully fill the toothed wheels of the oil pump, to avoid damage due to cavitation and to eliminate excessive noise, the pump housings are provided with crescent-shaped intakes at their suction side. Such an arrangement of the intakes, however, in conjunction with the specific configuration of the suction and pressure pipes as well as the oil grooves, does not permit the known oil pump to be used with both a clockwise or a counterclockwise rotating turbomachine without modifying the connection of the suction and pressure pipes with the pump housing.
It is an object of the present invention to provide an arrangement of suction and pressure pipe connections within an oil pump which can be used with a clockwise as well as a counter clockwise rotating turbomachine.
A further object of the present invention is to provide an oil pump having a pressure pipe line arrangement which prevents oil under pressure from flowing outside the pump housing.
These and other objects are achieved in the pump of the present invention wherein a pressure pipe is arranged inside a suction pipe that is disposed within a housing of the pump.
In the oil pump of the present invention, a pressure pipe is arranged concentrically within a suction pipe so that a vertical symmetrical axis of pinions of the oil pump coincides with a longitudinal axis of the pressure and the suction pipes. Such a concentric arrangement of the pressure pipe within the suction pipe simplifies an alignment of a circular profile of the suction pipe with the intake area of the suction duct, which is usually designed in rectangular shape and that leads to the toothed gear of the pump. By having the symmetrical axis of the oil pump coincide with the longitudinal axis of the pressure and suction pipes it is possible to use the pump with a turbomachine which rotates clockwise as well as with a turbomachine which rotates counterclockwise.
In accordance with a further object of the invention, the oil pump may be vented by having a connection lead from a pressure chamber of the oil pump to an oil-jet ejector. A suction chamber of the pump is then connected to the oil-jet ejector by means of a venting pipe and a check valve.
In accordance with a still further object of the present invention an oil sump which is supplied by the jet ejector is provided between a base support and the suction pipe. Since the oil sump is always filled with oil and since the suction pipe of the oil pump is mounted directly onto the base support with a metal contact and without the use of a gasket, the possibility that the oil pump will draw in air as a result of leakages is greatly reduced or eliminated.